Incipient Speciation in Freshwater Snails
Desert springs can be very useful as model systems for the investigation of speciation in aquatic organisms. The absence of other permanent habitat makes it possible to determine species' distributions very precisely. The springs may be isolated or semi-isolated, with population differentiation fostered by susceptibility to desiccation. This project is investigating an apparent case of speciation in progress in the Dalhousie Springs in the arid north of South Australia.
The gastropod genus Caldicochlea is endemic to springs. It contains two species, or species complexes, Caldicochlea harrisi and C. globosa that overlap morphologically but can be distinguished genetically. C. harrisi is found in many of the approximately sixty active springs in the seventy square kilometres of the Dalhousie complex, but C. globosa is concentrated in the larger, hotter springs in its northern half. The species occur together in many springs in this area, generally with apparently little or no hybridization. In two springs within the current ranges of both species, there is apparently free interbreeding. Reproductive isolation may have broken down in these springs or may not have been established in them. We are using allozyme electrophoresis and mitochondrial DNA sequencing to investigate which of these possibilities is correct.
Participants
Dr Winston Ponder, Centre for Evolutionary Research
Dr Don Colgan
Stephanie Clark (Malacology)
Themo Terzis
Copyright © 2003, Australian Museum
